Adding a Mailbox Server Role to Exchange 2010: "Database is mandatory on UserMailbox"

Dec 16, 2009

I came across an interesting error while adding a Mailbox Server to my Exchange Server 2010 environment the other day. The error was pretty clear-cut, and the solution was also pretty simple, but very non-intuitive, so I thought I’d explain how to fix it here. To give full credit, I got my answer from this dialog on the Microsoft TechNET forums, and the fellow with the username Nair.SS helped my solve the problem. It turns out another individual was having exactly the same problem, and he got his issue solved as well. Many thanks to Nair.SS.

The Error

The error message is pictured in this screenshot, and I’ve included the text in the caption:

Error Message when trying to add a mailbox server to Exchange Server 2010.

One important detail to include here is that I had two mailbox servers installed in this environment and I was unable to gracefully uninstall them. Thus I had to delete them out of Active Directory using ADSI Edit. I’m pretty sure this is what caused the problem.

The Fix

One of the mailboxes had incorrect settings in Active Directory, so I used ADSI Edit to edit that user.

I connected to the Domain well known Naming Context in my root domain and found the user named CN=FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042. I’m not sure if all those numbers will be the same for everyone, but you can just find the FederatedEmail **user. The **homeMDB property was blank, so I inserted the CN value of an existing database into the value field, formatted as such:

I went to install the additional mailbox role, and it installed without any problems. There was one other blog post found here that noted the particular error posted above, but the solution offered was different than mine. This error might have multiple solutions, but that post’s proposed solution did not work for me.

If you have anything to add, please leave it in the comments. Hope this helps!